METHOD FOR THE TREATMENT OF GAS

Abstract

A method for the treatment of gas generated by the combustion of fossil fuel in a first combustion chamber, the method comprising the steps of transferring the gas to a second combustion chamber, combusting the gas in the second furnace in the presence of oxygen and a fuel source to generate waste gas and treating the waste gas to produce a concentrated carbon dioxide stream.

Claims

1. A method for the treatment of gas generated by the combustion of fossil fuel in a first combustion chamber, the method comprising the steps of transferring the gas to a second combustion chamber, combusting the gas in the second combustion chamber in the presence of oxygen and a fuel source to generate waste gas and treating the waste gas to produce a concentrated carbon dioxide stream.

2. A method according to claim 1 wherein the gas is filtered to remove at least a portion of particulate material present in the gas prior to being transferred to the second combustion chamber.

3. A method according to claim 1 or claim 2 wherein the gas is compressed prior to entering the second combustion chamber.

4. A method according to any one of the preceding claims wherein the second combustion chamber comprises a furnace.

5. A method according to any one of the preceding claims the fuel source comprises a source of hydrocarbons.

6. A method according to any one of the preceding claims wherein an operating temperature within the second combustion chamber is higher than an operating temperature within the first combustion chamber.

7. A method according to claim 6 wherein the operating temperature in the second combustion chamber is between approximately 1200? C. and approximately 2400? C.

8. A method according to claim 6 or claim 7 wherein the operating temperature in the second combustion chamber is between approximately 1500? C. and approximately 2000? C.

9. A method according to any one of claims 6 to 8 wherein the operating temperature in the second combustion chamber is approximately 1800? C.

10. A method according to any one of the preceding claims wherein at least a portion of the heat generated by combustion of the gas in the second combustion chamber is used to drive one or more electricity generation devices.

11. A method according to any one of the preceding claims wherein at least a portion of the heat generated by combustion of the gas in the second combustion chamber is directed to the first combustion chamber.

12. A method according to any one of the preceding claims wherein the waste gas undergoes a separation process to separate certain gaseous components of the waste gas from other gaseous components.

13. A method according to claim 12 wherein one or more membrane filters are used to separate the gaseous components of the waste gas.

14. A method according to claim 12 or claim 13 wherein the separation process separates carbon dioxide from other gaseous components of the waste gas.

15. A method according to any one of the preceding claims wherein the concentration of carbon dioxide in the concentrated carbon dioxide stream is greater than 90% v/v.

16. A method according to any one of the preceding claims wherein the concentrated carbon dioxide stream is collected for sale and/or use.

17. A method according to any one of claims 1 to 15 wherein the concentrated carbon dioxide stream is treated in such a manner that carbon in the concentrated carbon dioxide stream is sequestered and therefore prevented from entering the atmosphere.

18. A method according to claim 17 wherein the carbon in the concentrated carbon dioxide stream is sequestered in synthetic rock, aggregate and/or building materials.

19. A method for the treatment of flue gas generated by the combustion of coal in a coal-fired power station, the method comprising the steps of combusting coal in a first furnace, collecting flue gas exiting the first furnace, compressing the flue gas to form a compressed gas, transferring the compressed gas to a second furnace, combusting the compressed gas in the second furnace in the presence of oxygen and a fuel source to generate waste gas and passing the waste gas through one or more separation membranes to produce a concentrated carbon dioxide stream.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0073] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

[0074] FIG. 1 illustrates a schematic diagram of a method for the treatment of gas according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0075] In FIG. 1 there is illustrated a schematic diagram of a method for the treatment of gas according to an embodiment of the present invention. The method includes a coal-fired power station including a first combustion vessel 10 in the form of a coal-burning furnace. Flue gas leaving the furnace 10 is directed to one or more sensors 11 for sensing the type and quantity of constituent gases in the flue gas. Information gathered by the one or more sensors 11 is fed to an information collection system (not shown), such as a computer, DCS, Scada or the like. Information collection is carried out in real time as the flue gas leaves the furnace 10.

[0076] After this, the flue gases are directed to a filtration system 12 in order to remove substantially all of the particulate matter from the gas. The particulate matter is collected and disposed of, although the method of disposal is dependent on the composition of the particulate matter.

[0077] Once the particulate matter has been removed from the gas, the flue gas is compressed in a compressor 13, before being directed to a storage tank 14.

[0078] When required, the compressed flue gas is transferred from the storage tank 14 to a second combustion chamber 15 in the form of a second furnace. The flue gas, and in particular the hydrocarbon content of the compressed flue gas, is combusted in the second combustion chamber 15 in the presence of oxygen supplied from an oxygen tank 16 and a hydrocarbon fuel supplied from a fuel tank 17.

[0079] The second combustion chamber 15 is also provided with an electrical ignition system 18 to assist in the ignition of the mixture in the chamber 15. The electrical ignition system 18 may be operated continuously, or may be operated only when required (such as when restarting the furnace 15 after a shutdown). In embodiments of the invention in which the electrical ignition system 18 is operated continuously, the electrical ignition system 18 may be operated with or without a pulsing function.

[0080] The information collection system (not shown) analyses the information collected by the one or more sensors 11 and compares it to programmed information to produce analysed data. The analysed data is then relayed to the electrical ignition system 18 which in turn controls the relative quantities of hydrocarbon fuel and oxygen released from the fuel tank 17 and oxygen tank 16, respectively, into the second combustion chamber 15.

[0081] Thus, by controlling the quantities of hydrocarbon fuel and oxygen fed to the second combustion chamber 15 based on the composition of the flue gas, the information collection system (not shown) is able to generate a mixture within the second combustion chamber 15 that is not only efficient in terms of generating a large amount of heat from the secondary combustion chamber 15, but will also minimise the generation of noxious or greenhouse gases.

[0082] Heat 19 generated by the combustion in the furnace 15 is used to create electricity in an electrical generator 20 (which may comprise a turbine and generator, or any suitable alternative), and the generated electricity is output to an electrical grid 21.

[0083] In the embodiment of the invention shown in FIG. 1, an efficiency control valve 22 directs a portion 23 of the heat generated in the second furnace 15 back to the first furnace 10, where it is used to generate steam in a boiler (not shown), the steam being used to drive a turbine (not shown) and generate electricity. By directing a portion 23 of the heat generated in the second furnace 15 back to the first furnace 10, the amount of coal required to be combusted in the first furnace 10 in order to achieve the necessary heat to operate the boiler (not shown) is reduced.

[0084] Waste gas 24 generated in the second combustion chamber 15 is directed to a scrubber (particularly a wet scrubber) or particle filter 25 to remove any residual particulate matter in the waste gas 24. In addition, passing the waste gas 24 though the scrubber or particle filter 25 acts to reduce the temperature of the waste gas 24.

[0085] The waste gas 24 leaving the scrubber or particle filter 25 is brought into contact with a first gas separation membrane 26. The membrane 26 is selectively gas permeable, meaning that certain gases (in this case, carbon dioxide) are able to penetrate the membrane 26 while other gases (including nitrogen, oxygen and so on) are unable to penetrate the membrane 26. Thus, the waste gas 24 is separated into a first concentrate stream 27 (which is relatively high in carbon dioxide) and a first reject stream 28 (which is relatively low in carbon dioxide). The first concentrate stream 27 is brought into contact with a second gas separation membrane 29, and, once again, certain gases (in this case, carbon dioxide) are able to penetrate the membrane 29 while other gases (including nitrogen, oxygen and so on) are unable to penetrate the membrane 29. Thus, the first concentrate stream 27 is separated into a second concentrate stream 30 (which has a higher carbon dioxide content than the first concentrate stream 27) and a second reject stream 31 (which is relatively low in carbon dioxide).

[0086] In the embodiment illustrated in FIG. 1, the second concentrate stream 30 represents the final concentrate stream as the carbon dioxide content of the stream has reached the desired level. The second concentrate stream 30 may then be further processed. For instance, the second concentrate stream 30 may be collected as liquid or gaseous carbon dioxide and used in any suitable application. Alternatively, the carbon dioxide may be sequestered in building products, synthetic rock or aggregate or the like in order to prevent the release of the carbon dioxide to the atmosphere.

[0087] The first reject stream 28 and the second reject stream 31 (both of which are low in carbon dioxide and high in gases such as nitrogen) may be released to the atmosphere through a flue or stack 32. If desired a portion 33 of the flue gas from the first combustion chamber 10 may also be released to the atmosphere.

[0088] A significant advantage of the present invention is that the addition of a second combustion chamber 15 and associated membranes 26, 29 does not require any redesign of an existing power station, and the additional equipment can be added to an existing flowsheet relatively easily.

[0089] In the present specification and claims (if any), the word comprising and its derivatives including comprises and comprise include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0090] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0091] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.